netplugd - Unix, Linux Command

NAME

SYNOPSIS

DESCRIPTION

netplugd
is a daemon that responds to network link events from the Linux
kernel, such as a network interface losing or acquiring a carrier
signal.

When an Ethernet-style network interface on a host is plugged into a
powered-up switch, hub, or other host, the two use a carrier signal to
establish that the link is alive. The Linux kernel makes this
information available through its
netlink(7)
interface.

The
netplugd
daemon listens for carrier detection and loss messages from the
kernels
netlink(7)
subsystem. When a carrier signal is detected on an interface, it runs
a script to bring the interface up. When carrier is lost,
netplugd
runs a script to bring the interface down.
netplugd
does not define any policies for how to manage interfaces; it leaves
that to a script,
/etc/netplug.d/netplug,
which is described in
FILES
below.

You tell
netplugd
which interfaces it should manage by giving it a list of shell-style
glob patterns, which it matches against using the
fnmatch(3)
function. For example, a pattern of
eth[13]
will tell
netplugd
to only manage
eth1
and
eth3,
if those interfaces exist. If the interfaces are not known to the
kernel at the time you start
netplugd,
perhaps because they are unplugged PCMCIA network interfaces or
devices whose drivers have not yet been installed,
netplugd
will start to manage them as soon as they are plugged in or their
drivers are available.

OPTIONS

Tag

Description

-F

Run in the foreground; do not detach and run as a daemon. Messages
are logged to
stdout
or
stderr,
instead of using the
syslog(3)
mechanism. This option is useful mainly for debugging your
configuration.

-P

Prevent autoprobing for interfaces. The
netplugd
daemon normally probes for all possible interface names that might
match the patterns you tell it to manage. This is necessary in order
to get network driver modules (the default with almost all Linux
distributions) loaded and set up, so that they can provide link status
notifications to the
netplugd
daemon. Autoprobing should always be safe, and doesnt take long.
Disable it with caution.

-c config_file

Specify the name of a file from which to read patterns that describe
the interfaces to manage. You can provide this option multiple times to read
from more than one file. If you do not provide this option at all,
netplugd
will attempt to read from a default config file. If you do not want
netplugd
to try to read from any real config files, you can specify
/dev/null
as a config file.

-i interface_pattern

Specify a pattern that will be used to match interface names that
netplugd
should manage. You can provide this option multiple times to specify
multiple patterns.

-p pid_file

Write the daemons process ID to the file
pid_file.
If you tell
netplugd
to run in the foreground, this option is ignored.

FILES

Tag

Description

/etc/netplug/netplugd.conf

Default config file to read, if none is specified on the command line.
The config file format is one pattern per line, with white space,
empty lines, and comments starting with a
#
character ignored. Patterns are standard shell-style glob patterns,
e.g. "eth[0-9]".

/etc/netplug.d/netplug

The "policy" program (typically a shell script) that
netplugd
uses to probe for interfaces, and to bring them up or down in response
to network link events. This program is called with the name of the
interface as its first argument, and one of the following options:

in

A cable was plugged in, or carrier came up. The command should bring
the interface up. The command is run asynchronously, and it should
exit with status 0 on success.

out

A cable was plugged out, or carrier went down. The command should
bring the interface down. The command is run asynchronously, and it should
exit with status 0 on success.

probe

The command should load and initialise the driver for this interface,
if possible, and bring the interface into the "up" state, so that it
can generate
netlink(7)
events. The command is run synchronously; it must exit with status
code 0 if it succeeds, otherwise with a non-zero exit code or signal.

Tag

Description

/etc/rc.d/init.d/netplugd

The
init(8)
script that starts, stops, and displays status of the
netplugd
daemon.

AUTHOR

COPYRIGHT AND LICENSE

netplugd
is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License, version 2, as published by
the Free Software Foundation. You are forbidden from redistributing
or modifying it under the terms of any other license, including other
versions of the GNU General Public License.

netplugd
is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.